1. Field of the Invention
The present invention is directed to a method for the operation of a medical X-ray installation of the type having at least one C-arm at which a solid-state image detector is rotatably arranged and also having a control device that controls the operation thereof.
2. Description of the Prior Art
In known X-ray installations, X-ray image intensifiers of different sizes are employed dependent on the application. In general angiography, for example, at least one X-ray image intensifier having a minimum diameter of 33 cm, preferably having a diameter of 40 cm, is necessary because of the field of view required for tracking a contrast agent bolus. In cardio-angiography, in contrast, smaller X-ray image intensifier formats such as, preferably, a 23 cm X-ray image intensifier are employed because the smaller size of the object to be image and particularly because of the high collision hazard of larger image intensifiers with the patient, for example given oblique projections. This leads to compromises in combination systems that are currently being more frequently employed. For example, a 33 cm X-ray image intensifier is actually too small for best results in general angiography; for cardio-angiography, in contrast, even the wide outside edge of the X-ray image intensifier is disturbing when, for example, a format as small as 14 cm or the 17 cm is employed.
Usually, therefore, X-ray systems employ a fixed arrangement of an X-ray tube and an image receiver wherein the spacing between these two components from one another can be variable, but the central ray always remains centered on the middle of the image receiver. In the case of slanting angulations, an image rotation may ensue, for example, by turning the video camera, so that the image remains in an upright position for the viewer.
The maximally possible projection angles are thereby predetermined by the mechanical dimensions of the components (for example, image intensifier housing). If used, possible collision protection control of the X-ray system also is matched to these fixed data.
In the case of mechanically large image receivers together with small zoom format, i.e. utilization of only a central, small region of the image receiver, a large xe2x80x9ccollarxe2x80x9d thus arises between the outside dimensions of the detector and the edge of the utilized image. The maximum angulation thus is not determined by the edge of the utilized image but by the basic mechanical arrangement.
Further, the use of solid-state image detectors in the framework of cardio-angiography is known. An added difficulty associated with the use of solid-state detectors, however, is that the rectangular or quadratic shape is disadvantageous in angulations in the event of a collision with the patient or some other object. It has been proposed to selectively employ a large or a small solid-state image detector dependent on the application. This, however, involves complicated mechanisms and leads to unacceptable costs.
PCT Application WO 01/45562 discloses an X-ray diagnostics installation with a collision detector that generates an alarm signal when the force exerted onto the movable parts exceeds a threshold.
An object of the present invention is to provide a method with which the advantages of a solid-state detector can be maintained while still allowing operation and in the framework of cardio-angiography with a zoomed image region that is smaller compared to the entire image converter format.
In a method of the type initially described, it is inventively achieved by turning or rotating the solid-state detector into an arbitrary position relative to the C-arm for the image pickup in order to avoid a collision, the potential collision risk being minimal in this arbitrary position, and wherein the image registered with the solid-state image detector is computationally rotated dependent on the position data of the solid-state image detector in order to enable a vertical presentation of the image at an output medium.
In accordance with the invention the solid-state image detector is rotated into an arbitrary position relative to the C-arm wherein it does no collide with the patient or some third object, for example the patient support table, so that the smallest unusable edge between the outside dimensions of the detector and the image area always arises in the desired position (angulation). This is especially important in the case of non-circular detectors since, for example, a corner thereof is likely to lead to a collision. In the position employed in the inventive method, there is usually the problem in conventional systems that the registered image no longer resides perpendicularly with reference to the longitudinal axis of the patient support table, so that it is displayed in rotated fashion at a monitor due to the rotated position of the solid-state image detector. In known systems, namely, the rotation of the solid-state detector always ensues such dependent on the projection angle of the C-arm such that the image always is presented upright with reference to the longitudinal axis of the table. The invention departs from this by allowing any arbitrary detector position. In order nevertheless to arrive at the standard image presentation desired by the physician, in the inventive method the registered image is computationally rotated, so that the image can be presented perpendicularly as usual, for example at the monitor. The computational rotation ensues dependent on the position data of the solid-state image detector relative to the C-arm, since the manner by which the registered image is to be rotated can be derived therefrom. This rotation can be implemented in real time by the available high-performance digital electronics, so that no disadvantages whatsoever occur for the attending physician. Due to the possibility of being ablexe2x80x94differing from known systemsxe2x80x94to rotate the solid-state detector into an arbitrary position relative to the C-arm, the detector can now be set such that it does not collide with the patient or the patient table or the like, but nonetheless can be moved as close as possible to the patient. Regardless of the format of the solid-state image detector, thus, arbitrary angulations are possible with the inventive method, so that an application-dependent change of detectors can be foregone.
In a further embodiment of the inventive method for optimizing the positioning possibilities of the solid-state image detector, the control device also determines that position or attitude of the zoom region of the solid-state image detector wherein the collision risk is lowest. To that end, an image field at the edge of the detector from the full image area of the detector given zoom is always employed, so that the smallest possible distance between the current image edge and the mechanical edge of the detector always arises. According to this embodiment of the invention, thus, the zoom possibility of the solid-state image detector is also utilized within the framework of the inventive method so that the control device not only determines the optimum rotated position but also, in conjunction therewith, determines the optimum positioning of the zoom region, or links the two with each other in order to thus determine the optimum position of the two with reference to the geometry of the detector as well as the geometry of the patient. When zooming occurs, the position data of the position of the zoom region also enter into the subsequently undertaken, computational image rotation.
The inventive method can be employed both in X-ray installations with a C-arm and in bi-planar X-ray installations. In this latter instance, i.e. when two separately movable C-arms each with a solid-state image detector are provided, the position data of the other solid-state image detector can be inventively taken into consideration in the determination of the positioning of the first solid-state image detector and, of course, its zoom region. Thus, the inventive method also allows a collision-free motion of the detectors taking the respective position of the two detectors into consideration in bi-planar systems as well.
Inventively, relevant data can be supplied by one or more collision sensors or by a collision calculation program in order to determine the position data of the solid-state image detector and of the zoom region.
The invention also is directed to a medical X-ray installation having at least one C-arm at which a solid-state image detector is rotatably arranged as well as having a control device. In accordance with the invention the control device of the X-ray installation is fashioned for determining that position of the solid-state image detector lying arbitrarily relative to the C-arm wherein the collision risk of the solid-state detector with an image object is at its lowest, and the control device also is fashioned for rotating the image registered with the solid-state image detector such that the image of the examination region can be displayed in a vertical position at an output medium.
In an embodiment of the inventive X-ray installation, the control device also determines the position of the zoom region of the solid-state image detector wherein the collision risk of the solid-state image detector with a third object is lowest, with the respective positions of the solid-state image detector and the zoom region of the detector being referred to one another in this case, so that a position that is as close as possible relative to the patient can be achieved overall.
Further, a number of collision sensors can be provided in the inventive X-ray installation, these supplying data relevant for the determination of the positions of the solid-state image detector and, possibly, of the zoom region. Alternatively, a calculation program can be used for supplying data relevant for the determination of the position data of the solid-state image detector and, possibly, of the zoom region.
The X-ray installation can be a bi-planar installation, wherein the control device is fashioned for the determination of the position data of one solid-state image detector and of its appertaining zoom region dependent at least on the position data of the other solid-state image detector.